Displacement of the Gent/1999 human-like swine H1N2 influenza A virus lineage by novel H1N2 reassortants in Germany

A swine influenza survey was conducted between 2003 and 2015 in Germany. During this period, 8122 snout swabs or other respiratory specimens from pigs of 5178 herds, mainly from Germany, were investigated for the presence of swine influenza A virus (S-IAV). In total, 1310 S-IAV isolates were collected. Of this collection, the complete genome of 267 H1N2 S-IAV isolates was sequenced and phylogenetically analyzed. The data demonstrate the incursion of human-like swine H1N2 viruses (Gent/1999-like) in 2000 and prevalent circulation until 2010. From 2008 onward, a sustained and broad change of the genetic constellation of the swine H1N2 subtype commenced. The Gent/1999-like swine H1N2 viruses ceased and several new swine H1N2 reassortants emerged and became prevalent in Germany. Of these, the upsurge of the Diepholz/2008-like, Emmelsbuell/2009-like and Papenburg/2010-like viruses is notable. The data reveal the importance of reassortment events in S-IAV evolution. The strong circulation of S-IAV of different lineages in the swine population throughout the year underlines that pigs are important reservoir hosts.